This invention relates to the production of superplastically formed metal alloy panel structures, and is more particularly directed to a novel superplastic forming and braze bonding process which permits the use of a broader range of metal alloys than is feasible with the superplastic forming/diffusion bonding processes of the prior art.
The fabrication of a built-up panel structure by mechanical assembly of multiple metal parts is costly, and typically requires joining hardware which adds considerable weight and complexity to the structure. This is a particularly critical issue in the aerospace industry, where weight is an extremely important consideration. Panel structures fabricated by superplastic forming and diffusion bonding (SPF/DB) processes such as those disclosed in U.S. Pat. Nos. 4,217,397 and 5,141,146, both assigned to McDonnell Douglas Corporation, for example, have offered significant reductions in both cost and weight. However, aluminum and some other alloys are limited in their diffusion bonding capabilities due to surface oxidation or other metallurgical phenomena, and have thus not been suitable for fabrication of SPF/DB panels.
What is needed, therefore, is a novel and unique process which will permit the production of single piece structures using aluminum or other diffusion bond resistant alloys in a manner similar to that of the SPF/DB process, such that the fabrication cost will be relatively low and the part weight can be significantly reduced with respect to comparable built-up structure.